1. Field of the Invention
This invention relates to an injection molding method for producing a packaged molded article by completely sealing a sheet-like component part such as a printed-circuit board with resin material.
2. Description of the Prior Art
In recent years, there have been supplied sheet-like indicators such as a resonant tag which is made by printing a resonant circuit (LC) on a printed board (including a flexible substrate). Under certain circumstances, a sheet-like indicator completely sealed with resin material has been needed according to usage, but a conventional indicator airtightly sealed is insufficient.
An airtight-sealing method and a resin-sealing method for sealing or enclosing semiconductor elements have been conventionally known. These sealing methods principally serve to protect or secure the semiconductor elements onto a printed board. In general, a low-pressure transfer molding method which may be deemed as an insert molding method has been adopted as the sealing method.
Incidentally, there has been so far known a laminated injection molding technique (including a molding die) adopting an insert molding method or a multi-material and multi-color molding method for completely sealing a monolithic component.
For example, Japanese Patent Publication No. HEI 6-49307(B2) discloses a two-layer injection molding method using a molding die which comprises a stationary mold, a movable mold, and a slidable mold mounted between the stationary mold and movable mold. The slidable mold is provided with first and second cavities, so that upon molding a central core primary molded piece) in the first cavity in primary molding, the slide mold is transferred for performing secondary molding in the second cavity without removing the central core molded in the first cavity, thus to form a surface layer around the central core. This prior art injection molding method makes it possible to continuously produce molded articles having the central core sealed in the surface layer formed secondarily in the second cavity.
That is, in the conventional molding method mentioned above, the primary molded piece formed in the slide mold in the primary molding is subjected to the secondary molding in the same slide mold without being removed from the slide mold. Accordingly, it is difficult for this conventional molding method to completely seal, with resin material, another component part such as a printed-circuit board to be given from the outside of the slide mold and inserted in the second cavity when carrying out the secondary molding. Thus, the conventional molding method is unable to easily produce molded articles (secondary molded pieces) sealed with resin material.
Also in Japanese Patent Publication No. HEI 2-38377(B2), there is disclosed a molding method for producing hollow molded articles, in which a slide mold is moved in a molding die so that primary molding is performed at a first position and secondary molding is performed at a second position. This prior art does not describe or in any way hint at a resin-sealing technique.